For example, in JP-A-11-258019 (Patent Literature 1), disclosed is that in measuring instruments such as a thermal type flow sensor, a housing that has measuring devices built-in and a cover that covers them are welded without the use of an adhesive agent. Further, for example, in JP-A-2007-210165 (Patent Literature 2), disclosed is a technology for welding a housing and a cover by laser. In JP-A-2010-162587 (Patent Literature 3), disclosed is that when another member is fixed to electronic equipment or a flow sensor by a thermal fusion bonding process including laser, a flow passage holding body is provided with heat insulation parts in order to suppress an effect of heat onto a circuit board or the like.